In most radio communication systems, communication service will tend to be obstructed by the reception of signals transmitted from other communication devices operating on or substantially at the same channel as the desired communicating channel. This phenomenon, often referred to as co-channel or in-channel interference occurs frequently in frequency modulated (FM) radio systems such as cellular radiotelephone communication systems, cord-less telephone systems, microwave communication systems, satellite communication systems and television transmission systems, just to name a few. Due to the pervasiveness of the phenomenon, the prior art reflects several methods and devices designed to overcome the problems associated therewith. Two commonly suggested approaches are resource management (i.e., avoidance) and detection/correction.
Resource management schemes attempt to distribute communication resources in a fashion that reduces the likelihood of an occurrence. For, example, cellular communication systems typically employ elaborate frequency reuse schemes, whereby interfering-channels are separated by large geographic distances in order to improve the ratio of desired signal to undesired signal reception. It is a well established practice in the art that this ratio, also known as the carrier-to-interference (C/I) ratio should provide a 15-18 dB range of separation between carrier and interfering signals in order to promote adequate system performance.
Other resource management solutions range from simply adding additional communication resources, i.e., increasing system bandwidth, to the narrowing of the desired communication channel. While, both approaches may have merit, they often prove too impractical for general applications. For example, system bandwidth is a finite commodity, the cost of which places practical limitations on availability. Narrower channel selection, while providing marginal improvements, nevertheless operates to decrease overall data throughput.
Detection/correction methods tend to address in-channel interference after the fact. A prior art detection device is disclosed in U.S. Pat. No. 4,998,289 assigned to the assignee of the present invention. Upon detection in the above-cited reference, a decision is made by an associated communications device whether to switch to an alternate communications channel.
While the above mentioned methods all attempt to minimize the impact of in-channel interference, they nonetheless fail to resolve the core issue; device sensitivity. It would be extremely advantageous therefore to provide a communication device architecture capable of operating at C/I ratios of less than 15 dB.